The invention set forth in this application pertains to new and improved pipe tapping tools which are especially adapted to be used in making so-called "hot taps" through a lateral or branch pipe into a main pipeline or distribution conduit.
The utility of the present invention is best explained by briefly referring to the manner in which various fluids such as natural gas and the like are commonly distributed. Normally such fluids are distributed through a main pipeline or conduit extending under a road or street. Such a fluid is normally distributed to individual users through a branch pipe or lateral extending off of such a conduit at various locations. As such principal pipes or conduits are installed frequently no laterals are connected to them since it is frequently unknown as to where such branch pipes or laterals should be located. Frequently after such a principal pipe or conduit is in use branch pipes or laterals are secured to it at various locations and holes are drilled or bored from the interior of the branches or laterals so as to establish fluid communication.
Such a process is referred to as "tapping" into the principal pipe or conduit. Such a tapping operation is frequently referred to as a "hot tapping operation" when the principal pipe or conduit contains a fluid such as gas under pressure. Specialized equipment has been developed for making so-called "hot taps" since it is necessary to prevent the loss of pressure from the principal pipe or conduit as a hole is being established between the lateral and such principal pipe or conduit. Such a tool either must be constructed in such a manner or utilized with auxiliary equipment so that the tapping part of the tool can be withdrawn from the lateral and so that the lateral may be connected up with an appropriate supply line or pipe without fluid escaping from the piping system.
In the past a number of different types of tools have been developed for making so-called hot taps. A recognition of the unique character of so-called "plastic" polymer pipes and a recognition of the desirability of using such pipe in distributing various different diverse fluids has resulted in a recognition of the desirability of utilizing tapping tools which are specifically adapted to be used with such plastic pipe. A number of such hot tapping tools for use with plastic pipe have been developed and to various extents used. An understanding of the present invention is not considered to require a detailed consideration of such prior specialized tools for use in making hot taps with plastic pipe.
However, it is considered important to note that the invention set forth in this specification is an outgrowth of sealing problems encountered with certain of such structures. Such structures have been constructed so as to utilize a plug-type body carrying appropriate sealing rings which is dimensioned so as to fit within an end of such a service branch or lateral so as to form a seal with the interior of it. These prior hot tapping tools have used a boring bar rotatably supported by such a plug-type body in such a manner as to be capable of being moved linearly and have used various different structures for mounting such a plug-type body against linear movement on a lateral or branch pipe both during manipulation of the boring bar and after a hole has been created in the principal distribution pipe or conduit.
The sealing problem encountered with such prior hot tapping tools has been determined to be normally related to such mounting structures. More specifically it has been found that such mounting structures have held the plug-type bodies indicated in the preceding discussion in such a manner that under service or use conditions such plug-type bodies have been capable of shifting slightly relative to a service pipe or lateral to a sufficient extent so as to affect the operation of the sealing rings carried by such a plug-type body. While in one sense the amount of leakage on occasion encountered as the result of this is minor, in another sense such leakage is quite significant. This is best illustrated with reference to the use of hot tapping tools in making hot taps into lines containing a fluid such as natural gas under pressure. The escape of even a small amount of such gas as the result of a seal improperly functioning can easily create a severely hazardous situation.